64K text fields cannot be used in advanced search, DB rules, UI rules, neither can they be audited. This is because, the 64K fields can hold large amount of data and any search on such a large field can have adverse impact on the DB/OVSD. Even history is a 64K field and hence, we cannot use the history field in any of the search, rules, etc.
I don't think we have an alternate solution. Or at least, I am not aware of.
As far as I am aware but I could well be out of date, you cannot search 64kB fields if using an Oracle DB as it is Oracle that does not allow it. If using a SQL server DB, I have used sd_dataform to search in a smart action.